The present invention relates to power converters, and more specifically, to power converters driving controllable inductors.
Converters using linearly controllable inductors rely on magnetic structures such as, for example, a double E-core 100 as shown in FIG. 1 having a main coil 102 bound around a gapped center leg of the core 100 and two series connected auxiliary coils 104 with the same number of turns wound around outlying legs. Two main windings (not shown) may be wound on each side of the air gap to reduce wire losses caused by fringing flux. The auxiliary coils generate flux in the same direction in the outer legs and in the opposite direction in the center leg. Flux cancellation in the center leg results in no net flux in the main coil. Neglecting non-linear effects, the coupling between the main and series connected auxiliary winding approaches zero.
Previous methods for generating control current include both linear and switch-mode power circuits that generate current in the control winding of the inductor.